"I had paid close attention to what Bush and Cheney had said in the campaign. I knew they saw the world very differently from the way I did and would want to undo much of what I had done, especially on economic policy and the environment."

The bloody carnage in Orlando, where a gunman at a gay nightclub killed 49 and wounded dozens more, underlined again how differently Obama and The Donald view the world.

As Obama, in his now far too familiar role as 'consoler-in-chief' reacted to the dreadful news with a calm and stately hand, Trump, the presumptive GOP nominee, went in strong on his favoured Twitter platform.

Trump effectively blamed radical Islam and Obama for the attack, and continued his calls to temporarily ban Muslims from entering America. He demanded Obama step down immediately for not using the term "radical Islam" to define the Orlando mass shooting.

Today, Trump continued his assault on Obama, in a speech heralded as the billionaire businessman's first major foreign-policy address.

"Truly, our president doesn't know what he's doing. He's failed us, and he's failed us badly. And under his leadership, this situation will not get any better, it will only get worse, and I've been saying that for a long time," he said.

In 2011, Trump put himself front and centre of the "birther" movement — a group of conspiracy theorists who were certain Obama's American birth certificate was a fake, and that he was actually born in Kenya.

Trump famously began to tour US talk shows and publically demand the president release his birth certificate. At "peak birther", Trump signalled his intent to send private investigators to Hawaii to find alleged holes in Obama's back story and blow open the supposed cover up.

Such is the historical niggle between the pair, Obama's note may contain just two very short words, should the New York tycoon beat the odds and take charge of the Oval Office.